Microsoft, it seems, is relegating the Zune to storage duty. A survey in the Zune newsletter mentions something about using the Zune hard drive for extra Xbox hard drive storage, something that is currently impossible. I originally thought they meant that they were asking about using the Zune to play music through the Xbox but the second question mentions that usage scenario. This might be a slip up, but it also might be a great way to add storage to an Xbox for relatively cheap.
The Zune is, after all, little more than a fat hard drive. While it’s not the best idea to store huge games on your Zune, you could possibly put your gamer profile on there and some saved games so you can visit your friend and finish up GoW 2 in tandem. Who knows.